The present invention relates generally to electric fence charger (i.e., electric fence box) protection systems. More particularly, this invention pertains to protecting electric fence boxes from lightning.
Electric fences are used by ranchers and farmers to keep animals in a designated area or out of a designated area. Electric fences include a first length of conductive material (i.e., the fencing) isolated from earth ground by insulators. The fence may also include a second length of conductive material connected to earth ground and spaced apart from the first length of conductive material. The first length of conductive material is connected to a first output of the electric fence box, and the second output of the electric fence box is connected to ground, and optionally to the second length of conductive material. The electric fence box is subject to damage from power line voltage spikes which can cause a surge in input current. Most electric fence boxes include fuses (e.g., round body 125V, 10 A fuses) to prevent over-current conditions from power line surges from damaging the fence box. The power surge burns out the filament in the fuse before the increased voltage and current can damage the electronics in the electric fence box. The largest standard fuses only have about 3 inches between contacts, but even a millimeter of separation between contacts is enough to prevent a 125V source from arcing between the contacts. The electric fence box is also subject to damage from lightning striking the fence. Lightning is a static charge that travels along the length of conductive material to the electric fence box. Lightning develops voltages much higher than 125V and can jump from one electrical contact to another across hundreds of feet. The 0.5″ to 1″ gap between the contacts in most standard fuses, and even the 3″ gap between contacts available in some industrial fuses is not enough to prevent arcing between the contacts. Lightning typically arcs between the contacts in electronic fence box fuses and destroys the fence box when the lightning strikes the electric fence charged by the electric fence box.